Method of adjusting print magnification in digital duplex printing

ABSTRACT

A method of adjusting print magnification in digital duplex printing in which the difference in print magnification from front to back side is measured on a text sheet and the percentage difference calculated. Provision is made for user inputs for adjusting the digital image print magnification laterally and longitudinally whereupon changes are evaluated in another text printing.

BACKGROUND

The present disclosure relates to printing of digital images andparticularly printing by an electrostatic or xerographic process inwhich an image is generated on a photoreceptor and transferred to aprint media sheet and heat fixed thereon. More particularly, thedisclosure relates to duplex printing of digital images by theelectrostatic processor printing on both sides of the print media sheet.

With the advent of electrostatic photocopiers capable of relatively highproduction rates, these machines have found particular suitability toprinting of documents requiring duplex printing where the individualsheets or pages are subsequently bound into books or pamphlets and thelike. However, in duplex printing of sheets or pages intended forbinding, in order to provide a quality print job which is competitive inthe market place, it is necessary that the print on both sides of thepages be registered or positioned on the page such that there is nonoticeable variation to the reader of the print on the page from thefirst to the second side. It has been found that variations of 2 mm orless in the image registration from Side 1 to Side 2 of a sheet or pageare quite noticeable to the eye of the reader and give the impression ofa poor quality print job. Accordingly, it has been found necessary tomaintain very tight control of the image magnification or registrationin duplex printing from Side 1 to Side 2, or front to back, of theprinted media sheet.

Maintaining the aforesaid tight control of print magnification from Side1 to Side 2 in a duplex printing job on an electrostatic photocopier hasproven to be difficult and costly in such machines set up for high speedduplex printing. This has been found to be the case irrespective ofwhether the digital image is transferred directly to the electrostaticprinting machine such as from a computer or is generated from a printedsheet inputted for copying and reproduction. The complexity of theprocesses within the electrostatic print engine including the transportof the paper through the sheet path and heat fusing in the print enginehas introduced error in the print magnification and registration fromSide 1 to Side 2 on a printed sheet.

Accordingly, it has been desired to provide a way or means of enablingthe user to control the quality of the duplex printing with respect tothe image magnification and registration on the printed sheet; and,particularly it has been desired to provide the user with a way or meansof correcting errors in the print magnification by varying the printingprocess.

BRIEF DESCRIPTION

The present disclosure describes a method of enabling the user to adjustthe printing process in an electrostatic printer to correct errors ofprint magnification and registration in duplex printing for maintainingthe quality of the print job and particularly for controlling printmagnification such that the reader of the printed document will notnotice variation in the magnification or registration of the imagesprinted on Side 1 and Side 2 of the printed sheet or page.

The presently described and illustrated method provides a user inputpanel or interface on an electrostatic reproducing machine upon whichthe user may enter commands for incrementally changing the longitudinaland lateral magnification of the digital image prior to printing. Theuser is enabled to determine the desired amount of correction for theprint magnification by running a test print and measuring the variationof the print magnification and registration from Side 1 to Side 2, orfront to back, of a printed sheet. The percentage change from front toback is then computed; and, the user can input a desired number ofpredetermined incrementally small changes in the percentage ofmagnification and view the results on another test print. Once the testprints confirm that the correct preprint magnification corrections havebeen made to the digital image, the print job may be run in itsentirety.

In one embodiment of the method described in the present disclosure, theuser inputs the desired corrections for print magnification by analogcontrols such as, for example, rotating control knobs to a positionindicated for the desired amount of correction. In another embodiment ofthe method described and disclosed herein, the user input panel providestouch screen digital entry of desired amounts of print magnificationcorrection. The method of the present disclosure is described in anexemplary embodiment wherein the user desired corrections are inputtedto the digital front end (DFE) or controller for changing the operationof a raster image processor (RIP) prior to printing on the respectiveSide 1 and Side 2 of the sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a side view of a typical photocopying machine showing thelocation of the user input panel with the housing broken away to showthe paper path through the print engine;

FIG. 2 a is a section view taken along section indicating lines 2-2 ofFIG. 1 and shows the digital version of the user input panel;

FIG. 2 b is a view similar to FIG. 2 a of an analog version of the userinput panel;

FIG. 3 is a block flow diagram of the method of the present disclosure;and,

FIG. 4 is a block flow diagram of an exemplary embodiment of the methodof FIG. 3.

DETAILED DESCRIPTION

Referring to FIG. 1, a xerographic photocopying/printing machine isindicated generally at 10 and includes a sheet feeder 12 for providingautomatic feed of print media sheets along a path 13 to a raster opticalscanner (RAS) 14 which receives the image from a raster image processor(RIP) 16 and generates the image on a first photoreceptor 18. The imageis then transferred from the photoreceptor 18 onto the print media sheetand fed through a path 20 to a fuser 22 for securing the image on thesheet. The sheet then is fed to an inverter 24 which supplies the sheetalong path 26 to a second raster optical scanner receiving an image fromthe raster image processor 16. The scanner 28 generates an image on thesecond photoreceptor 30 which transfers the image to Side 2 of the sheetwhich is fed along path 32 to a fuser 34 for securing the image on Side2 of the sheet. Alternatively, the sheet may be fed from the inverterback to the first photoreceptor for printing on the second side therebyusing only one photoreceptor where it is desired to provide a lesscostly machine and where the resultant decreased productivity isacceptable. The duplex printed sheet is then fed along a path 36 to areceptacle or tray 38 or alternatively to an automatic stacker 40.

The machine 10 includes a user input panel or console indicatedgenerally at 42 which has provision thereon for manually inputting, tothe digital controller or DFE 15 for the machine, desired corrections tothe print magnification which controls the raster image processor 16.

Referring to FIG. 3, the method is described with reference to a blockflow diagram wherein an initial duplex test sheet is printed at step 44;and, the user measures the print magnification on Side 1 and Side 2 ofthe printed sheet at step 46. The user then computes the percentagedifference between Side 1 and Side 2 print magnification in both thelateral and longitudinal directions at step 48; and, proceeding to step50, the user inputs the longitudinal and lateral print magnificationcorrections from the digital print controller user interface (ReferenceNumeral 42 in FIG. 1) as will hereinafter be described in greaterdetail.

At step 52, a new duplex printed test sheet is made and at step 54 theprint magnification on Side 1 and Side 2 is measured and the percentagedifference in magnification computed by the user. At step 56, adetermination is made by the user as to whether the print magnificationSide 1 to Side 2 is within acceptable limits; and, if the determinationis affirmative the print job is run at step 58.

However, if the determination at step 56 is negative, then it isnecessary to return to step 46 and measure the Side 1 and Side 2magnification and input a new set of corrections to the user interface42.

Referring to FIG. 2 a, an exemplary embodiment of a digital version ofthe user interface 42 is indicated at 60 and has a window or indicator62 for displaying the selected change in the lateral printmagnification; and, similarly, panel 60 has a digital indicator orwindow 64 for indicating the selected change in the longitudinal printmagnification. The windows 62, 64 are aligned under the designation forSide 1. Adjacent the window 62 are user tactile input devices such as,for example, pushbuttons or relatively small touch sensitive pads of thetype well know in the art, with one input device 66 for incrementallyincreasing the percentage change of the lateral magnification by 0.01percent and a second input device 66 for decrementing the lateralmagnification by 0.01 percent. Similarly, tactile input devices 68, 70are provided adjacent window 64 for incrementing and decrementing thelongitudinal magnification by 0.01 percent.

User input panel or console 60 also includes separate indicator windowsfor indicating the selected percentage change of the lateral andlongitudinal print magnification for Side 2 of the printed sheet; and,these are denoted respectively by reference numerals 72, 74 in FIG. 2 a.The panel 60 also includes tactile input devices 76, 78 disposedadjacent window 72 for respectively inputting incremental and/ordecremental changes of 0.01 percent to the lateral print magnificationfor Side 2. Adjacent window 74 is a pair of tactile input devices 80, 82operative for the user inputting respectively an increment and adecrement of 0.01 percent change in the longitudinal magnification ofSide 2.

Referring to FIG. 2 b, another exemplary version of the user interface42 is indicated at 84 and has a rotatable knob 86 disposed thereon withjuxtaposed indicia for selecting a desired lateral percentage change inlateral print magnification. The knob 84 is user rotatable in theclockwise direction for incrementing the percentage change in 0.01percent increments; and, the knob 86 is rotatable in a counterclockwisedirection for decrementing the percentage change in lateral printmagnification by 0.01 for each position indicated.

Console 84 has a second knob 86 disposed below knob 84 for user rotationto provide incremental and decremental changes in the percent oflongitudinal print magnification by amounts of 0.01 percent for eachposition of the knob rotation. The clockwise rotation of the knob 86provides increments of 0.01 percentage change and counterclockwiserotation of the knob 86 providing decremental changes of 0.01 percent oflongitudinal print magnification.

Adjacent the right hand side of the console 84 in laterally spacedarrangement is disposed a pair of knobs denoted 88, 90 arranged oneunder the other for user inputting corrections for print magnificationin the printing of Side 2 of the duplex printed sheet. The upper knob 88is rotatable clockwise for incrementing the lateral print magnificationof Side 2 by 0.01 percent for each indicated position of the knob; and,knob 88 is rotatable counterclockwise for decrementing the lateral printmagnification by 0.01 percent by each of the rotary positions indicated.

The lower knob 90 is similarly rotatable clockwise for incrementing by0.01 percent, for each rotary position indicated, the longitudinal printmagnification of side 2 of the duplex printed sheet. Counter clockwiserotation of knob 90 provides decrementing of 0.01 percent oflongitudinal print magnification for Side 2 of the duplex printed sheet.

Referring to FIG. 4, an exemplary version of the method of the presentdisclosure is indicated in block flow diagram where at step 92 the userinputs desired changes to the user interface at step 94 to the systemcontroller or digital front end at step 96 which provides theappropriate signal to the raster image processor (RIP) at step 98. TheRIP 98 generates an electrostatic image on the photoreceptor at step100; and, the print engine 10 is operative to transfer the image createdin step 100 to Side 1 of the print sheet at step 102. The sheet is thenfed to the fuser at step 104 the image secured and the sheet moved alongthe path to the inverter at step 106 which inverts the sheet and feedsit, trailing edge first, along a path to a second RIP at step 108, whichgenerates an image in the second photoreceptor on the Side 2 of thesheet at step 110. The image generated at step 110 is then transferredto Side 2 of the print sheet at step 112 and fed along a path to thefuser at step 114 where the image is secured on Side 2 of the printsheet. The user then measures the Side 1 and Side 2 print magnificationat step 116; and, at step 118 the user makes the determination whetherthe print magnification measured in step 116 is within the desiredlimits or whether correction is needed. If the determination in step 118is affirmative, the user then again returns to step 92 and inputsadditional corrections. However, if the determination at step 118 isnegative, duplex print job is then completed at step 120.

The present invention thus provides a method of duplex printing in anelectrostatic or xerographic printer with a user interface which permitsentering corrections to the print magnification both laterally andlongitudinally for Side 1 and Side 2 of the printed sheet based upon theuser's measurements from a test print of the print magnificationproduced by the existing settings of the machine.

It will be appreciated that various of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be desirablycombined into many other different systems or applications. Also thatvarious presently unforeseen or unanticipated alternatives,modifications, variations or improvements therein may be subsequentlymade by those skilled in the art which are also intended to beencompassed by the following claims.

1. A method of adjusting print magnification in digital duplex: printingcomprising: (a) printing a duplex print sheet; (b) measuring thedifference in print magnification from Side 1 to Side 2 of the printedsheet and calculating the percentage difference; (c) providing for userinputs and adjusting the digital image print magnification of Side 2 andcompensating for the difference; and, (d) printing another duplex testprint sheet and determining whether further adjusting is required. 2.The method defined in claim 1, wherein the step of providing for userinputs includes providing for one of moving an analog control member andentering digital inputs.
 3. The method defined in claim 1, wherein thestep of providing for user inputs includes displaying on a screen andthe step of providing for user inputs includes providing for tactileinputs.
 4. The method defined in claim 1 wherein the step of measuringincludes measuring differences in lateral and longitudinal directions;and, the step of calculating the difference includes calculating thepercentage difference in the lateral and longitudinal directions of theprinted sheet.
 5. The method defined in claim 4, wherein the step ofadjusting includes adjusting for print magnification in the lateral andlongitudinal directions of the printed sheet.
 6. The method defined inclaim 1, wherein the step of adjusting includes adjusting the digitalfront end (DFE).
 7. The method defined in claim 1, wherein the step ofadjusting includes adjusting the scan rate of a raster image processor(RIP).